title: Retinal mean transit time determined with an impulse-response analysis from video fluorescein angiograms.
abstract: OBJECTIVE
  To evaluate a new technique for determining the Mean Transit Time (MTT) of retinal circulation, based on an impulse-response analysis. The results obtained were compared to those obtained with a conventional method based on semilogarithmic extrapolation.
  
  
  METHODS
  128 frames at a rate of 5 frames per second were digitized from video fluorescein angiograms and processed with a specially designed image analysis system. The MTT was determined from 25 curve pairs from 12 eyes in 8 young, healthy volunteers by the conventional technique (MTT[SLOPE]) and by our newly developed Impulse-Response analysis (MTT[IR]).
  
  
  RESULTS
  MTT(SLOPE) and MTT(IR) calculated for the 25 curve pairs were 3.54 +/- 1.00 and 2.67 +/- 0.88 seconds, respectively (Mean +/- SD). There was a good correlation between the two techniques (r2 = 0.81, p < 0.001). Unlike MTT(SLOPE), MTT(IR) could be calculated also from curves with a badly defined bolus.
  
  
  CONCLUSIONS
  We conclude that MTT(IR)-analysis of the retinal circulation may be used for clinical studies on retinal blood flow from angiograms obtained in patients.
authors.affiliation: Department of Physiology and Medical Biophysics, University Hospital, Uppsala, Sweden.
authors.forename: G O
authors.initials: GO
authors.lastname: Sperber
authors.forename: A
authors.initials: A
authors.lastname: Alm
mesh_terms: D001775:Blood Circulation; D001783:Blood Flow Velocity; D005451:Fluorescein Angiography / Q000379:methods*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D012171:Retinal Vessels / Q000502:physiology*